Integrated circuits are typically fabricated on wafers which are then cut up to form individual integrated circuits. These individual circuits are packaged within hermetically sealed ceramic or plastic packages. The signal and power lines from the integrated circuit are brought out to the pins of the package by means of leads attached to bonding pads on the integrated circuit chips. The chips are then used to form larger circuits by interconnecting the integrated circuit packages by means of printed circuit boards. These circuit boards may contain several layers of electrical interconnect. Typically the integrated circuit packages are soldered to the circuit board. The soldering process forms an electrical and mechanical connection between the integrated circuit package and the circuit board.
To form still larger circuits called modules, circuit boards may be arranged and interconnected in a variety of ways. One popular high density interconnect scheme is to stack the circuit boards in a sandwiched relationship and electrically interconnect the circuit boards with jumpers passed through the stack along the Z axis. This packing scheme achieves a relatively high packing density limited by heat dissipation and connector spacing requirements.
The aforementioned technique of forming larger circuits by using individually packaged integrated circuits mounted on circuit boards limits packing density. The actual integrated circuit chips themselves are typically smaller than one-tenth of a square inch, and only cover only 10-20 percent of the board area. Due to the low density achieved through the use of individually packaged integrated circuit chips and traditional interconnection technology, it is difficult to increase the operating speed of the system. Additionally, the inter-board spacing of stacked circuit boards is limited by the height of the integrated circuit packages and the inter-board connects. This limits packing density in the z direction as well. Configurations which limit packing density limit the interboard signal speed due to the long propagation delays associated with the long interconnect lines.
Another problem presented by traditional configurations relates to the ease with which modules can be disassembled. Forms of construction which involve soldering and staking of the board assemblies typically result in modules which cannot be disassembled or repaired.
The present invention provides a new apparatus and method for high-density interconnects of circuit boards which overcomes these disadvantages of the prior art.